There is a fusion splicing method as a method of connecting an end portion of an optical fiber and an end portion of another optical fiber. JP 2002-169050 discloses a fusion splicer for fusion-splicing an end portion of an optical fiber and an end portion of another optical fiber. This fusion splicer includes a pair of microscopes that observe side surfaces of the optical fibers from different angles. These microscopes are designed to be movable, and can accurately observe the cores of the optical fibers.